December 10, 2010

In the Spotlight – Revisiting a Disease Investigation with the GB Wildlife Disease Surveillance Parternship

Seasonal Increase of Trichomonosis in Garden Birds in Great Britain

There was a seasonal increase in the number of trichomonosis incidents diagnosed in garden birds this quarter, following the same temporal pattern as previous years: trichomonosis was suspected or confirmed in 46 of 73 garden birds (63%) examined at the IoZ this quarter.

These cases comprised two blackbirds (Turdus merula) (from two sites), one barn owl (Tyto alba), one bullfinch (Pyrrhula pyrrhula), six chaffinches (Fringilla coelebs) (from 5 sites), two collared doves (Streptopelia decaocto) (from two sites), one feral pigeon (Columba livia), two goldfinches (Carduelis carduelis) (from two sites), 26 greenfinches (Carduelis chloris) (from 24 sites), two sparrowhawks (Accipiter nisus) from two sites, and three wood pigeons (Columba palumbus) (from three sites). As in previous years, greenfinches appeared the most commonly affected species. Affected cases were received from across England and Wales.

The two affected blackbirds were submitted in July, from separate mortality incidents in which there were concurrent finch mortalities. The first of the two cases, which was from a Wiltshire garden, had been observed ill for approximately two weeks prior to death and had gradually developed severe torticollis (Figure 1). On post mortem examination there was a large, necrotic, caseous lesion adherent to the oesophageal wall (Figure 1), from which Trichomonas sp. was isolated. This lesion extended dorsally into the tissues of the vertebral column adjacent to the spinal cord.

Approximately ten finches (mainly greenfinches, also goldfinches and chaffinches) had been observed ill in the garden over the course of the year and up to the period that the blackbird was submitted. The second blackbird was submitted from a Lincolnshire garden, where it had been seen having difficulty feeding prior to death. There was a large, spherical, necrotic lesion on the caudal tongue consistent with trichomonosis (pending PCR confirmation). Approximately nine finches (mainly greenfinches, also chaffinches) had also been observed ill, or died, in the garden around the time that the blackbird died.

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